Power receiver circuit

ABSTRACT

Systems and techniques are provided for a power receiver circuit. A power receiver circuit may include power generating elements that may generate alternating current. The power receiver circuit may include group circuits that may connect power generating elements in parallel to combine the alternating current from the power generating elements into a single alternating current. The power receiver circuit may include rectifier circuits which may include rectifier channels connected to the group circuits and may include a rectifier that may generate direct current from alternating current. The power receiver circuit may include a step down converter connected to rectifier circuits that may convert direct current to direct current of a target voltage level. An output switch and linear regulator may be connected to the step down converter, and a microcontroller may be connected to the linear regulator and the output switch and may control the output switch.

BACKGROUND

Power generating mechanisms may deliver alternating current to a devicethat may run on direct current. The device may operate, or charge abattery, using the alternating current by converting it to directcurrent. The alternating current delivered by some power generatingmechanisms may have varying amplitudes, which may result in inefficientconversion of the alternating current to direct current.

BRIEF SUMMARY

According to implementations of the disclosed subject matter, a powerreceiver circuit may include a power generating mechanism includingpower generating elements that may generate alternating current signals.The power receiver circuit may include group circuits. Each groupcircuit may connect a group of power generating elements in parallel inan electrical circuit to combine the alternating current signals fromthe power generating elements in the group into a single alternatingcurrent signal. The power receiver circuit may include rectifiercircuits. Each rectifier circuit may include rectifier channels. Eachrectifier channel may be connected to one of the group circuits. Eachrectifier channel may include a rectifier that may generate a directcurrent signal from an alternating current signal, a switch bankincluding two or more outputs, and a maximum power point tracker (MPPT).The power receiver circuit may include a voltage bus includingcapacitors. Each capacitor may be connected to one of the rectifiercircuits. The power receiver circuit may include undervoltage lockouts.Each undervoltage lockout may have an input connected to one of thecapacitors and an output. Each undervoltage lockout may disconnect itsoutput when a voltage level input to the undervoltage lockout dropsbelow a predetermined threshold. The predetermined threshold may bedifferent for two of the undervoltage lockouts. The power receivercircuit may include DC/DC converters. Each DC/DC converter may beconnected to one of the undervoltage lockouts. Each DC/DC converter mayconvert a direct current signal of a predetermined voltage level to adirect current signal of a target voltage level. The predeterminedvoltage level may be different for two of the DC/DC converters.

A power receiver circuit may include a power generating mechanismincluding power generating elements that may generate alternatingcurrent signals. The power receiver circuit may include group circuits.Each group circuit may connect a group of power generating elements inparallel in an electrical circuit to combine the alternating currentsignals from the power generating elements in the group into a singlealternating current signal. The power receiver circuit may includerectifier circuits. Each rectifier circuit may include rectifierchannels. Each rectifier channel may be connected to one of the groupcircuits. Each rectifier channel may include a rectifier that maygenerate a direct current signal from an alternating current signal. Thepower receiver circuit may include a step down converter connected tothe rectifier circuits. The step down converter may convert a directcurrent signal to a direct current signal of a target voltage level. Thepower receiver circuit may include an output switch connected to thestep down converter. The power receiver circuit may include a linearregulator connected to the step down converter. The power receivercircuit may include a microcontroller connected to the linear regulatorand the output switch and that may control the output switch.

Systems and techniques disclosed herein may allow for a power receivercircuit. Additional features, advantages, and embodiments of thedisclosed subject matter may be set forth or apparent from considerationof the following detailed description, drawings, and claims. Moreover,it is to be understood that both the foregoing summary and the followingdetailed description are examples and are intended to provide furtherexplanation without limiting the scope of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the disclosed subject matter, are incorporated in andconstitute a part of this specification. The drawings also illustrateembodiments of the disclosed subject matter and together with thedetailed description serve to explain the principles of embodiments ofthe disclosed subject matter. No attempt is made to show structuraldetails in more detail than may be necessary for a fundamentalunderstanding of the disclosed subject matter and various ways in whichit may be practiced.

FIG. 1 shows an example system suitable for a power receiver circuitaccording to an implementation of the disclosed subject matter.

FIG. 2 shows an example system suitable for a power receiver circuitaccording to an implementation of the disclosed subject matter.

FIG. 3 shows an example system suitable for a power receiver circuitaccording to an implementation of the disclosed subject matter.

FIG. 4 shows an example system suitable for a power receiver circuitaccording to an implementation of the disclosed subject matter.

FIG. 5 shows an example system suitable for a power receiver circuitaccording to an implementation of the disclosed subject matter.

FIG. 6 shows an example system suitable for a power receiver circuitaccording to an implementation of the disclosed subject matter.

FIG. 7 shows an example system suitable for a power receiver circuitaccording to an implementation of the disclosed subject matter.

FIG. 8 shows an example system suitable for a power receiver circuitaccording to an implementation of the disclosed subject matter.

FIG. 9 shows an example system suitable for a power receiver circuitaccording to an implementation of the disclosed subject matter.

FIG. 10 shows an example system suitable for a power receiver circuitaccording to an implementation of the disclosed subject matter.

FIG. 11 shows an example arrangement suitable for a power receivercircuit according to an implementation of the disclosed subject matter.

FIG. 12 shows a computer according to an embodiment of the disclosedsubject matter.

FIG. 13 shows a network configuration according to an embodiment of thedisclosed subject matter.

DETAILED DESCRIPTION

According to embodiments disclosed herein, alternating current signalsof varying amplitudes may be efficiently converted to a direct currentsignal with a specified voltage. The alternating current signals may beconverted to direct current signals of different voltages depending onthe magnitude of each alternating current signal. The direct currentsignals of different voltages may then be converted to direct currentsignals of the same, specified, voltage, which may be combined into anoutput direct current signal of the specified voltage.

A power receiver circuit may be connected to a power generatingmechanism. The power generating mechanism may be, for example, an arrayof power generating elements. For example, the power generatingmechanism may be a transducer array, such as an optical transducer arrayor an ultrasonic transducer array including any suitable number ofultrasonic transducer elements, or a radio frequency (RF) receiver. Eachpower generating element may generate an alternating current signal ofvarying amplitude, and amplitudes and phases of the alternating currentsignals generated by different power generating elements may vary,resulting in alternating current signals of varying voltages. Forexample, ultrasonic transducer elements of an ultrasonic transducerarray may generate alternating current signals based on the movement ofa flexure, such as a piezoelectric flexure, in response to receivedultrasound waves. The amplitude of the alternating current signalsgenerated by an ultrasonic transducer element may vary as the amplitudeof the ultrasonic waves received by the ultrasonic transducer elementchange. Different ultrasonic transducer elements in the same ultrasonictransducer array may generate alternating current signals with differentamplitudes, resulting in the alternating current signals havingdifferent voltages. The alternating current signals may have variousphase shifts relative to each other.

The power receiver circuit may include a static input circuit. The powergenerating elements of the power generating mechanism may be connectedto the static input circuit. The static input circuit may include anysuitable number of group circuits, each connecting any suitable numberof the power generating elements in parallel. For example, an ultrasonictransducer array may include 256 ultrasonic transducer elements. Thestatic input circuit may include 64 group circuits, each of whichconnects a group of 4 ultrasonic transducer elements in parallelelectrically. Each group circuit may include its own output, which mayoutput an alternating current signal that results from combining thealternating current signals of the power generating elements connectedto the group circuit. For example, a static input circuit with 64 groupcircuits may include 64 outputs. The power generating elements in agroup connected to the same group circuit may be selected in anysuitable manner, such as, for example, physical proximity. For example,in an ultrasonic transducer array, 4 ultrasonic transducer elements thatare neighbors in a square may be connected to the same group circuit ofthe static input circuit. This may minimize the variance in theamplitude and phases of the alternating current signals generated by theultrasonic transducer elements and fed into the group circuit, as thephysical proximity of the ultrasonic transducer elements may result inthem receiving similar ultrasonic waves. The static input circuit andgroup circuits may be implemented in any suitable manner. For example,the static input circuit may be implemented through routing circuitry onlayers of a PCB which includes the power generating elements. In someimplementations, the group circuits may connect the power generatingelements in series.

The power receiver circuit may include any suitable number of rectifiercircuits. For example, there may be one rectifier circuit for every 32group circuits in the static input circuit. Each rectifier circuit mayinclude any suitable number of channels, which may be connected to theoutputs of the group circuits. The number of channels in a rectifiercircuit may be equal to number of group circuits connected to therectifier circuit. For example, a rectifier circuit connected to 32group circuits may include 32 channels, with each channel connected tothe outputs of one of the group circuits.

A rectifier channel may include a rectifier, a maximum power pointtracker (MPPT), and a switch bank. The rectifier may be an AC/DCrectifier of any suitable type. The rectifier be a full-wave bridgerectifiers with differential inputs. The rectifier may use a diodebridge, Schottky diodes, diode-connected FETS, or may be any form ofsynchronous rectifier. The rectifier may receive the alternating currentsignal from a group circuit of the static input network and may output adirect current signal of any suitable voltage.

The switch bank may include any suitable number of outputs, which maycarry a direct current signal received from the rectifier. Each of theoutputs of the switch bank may be assigned a different voltage level,and the switch bank may select only one output at a time to receive thedirect current signal from the rectifier. The direct current signal fromthe rectifier may be output from the rectifier channel through theselected output of the rectifier channel's switch bank. For example, aswitch bank may include five outputs, which may be assigned voltagelevels of 6 Volts, 10 Volts, 14 Volts, 18 Volts, and 22 Volts. Thevoltage of the direct current signal output by the rectifier may be, orbe within a range of, the voltage of the selected switch bank output.The outputs of the switch banks of the rectifier channels of a rectifiercircuit may be combined, so that the rectifier circuit may have a numberof outputs equal to the number of outputs of a single switch bank. Eachoutput from a rectifier circuit may be connected to outputs from theswitch banks of the rectifier channels that were assigned the samevoltage level. For example, a rectifier circuit with 32 rectifierchannels with switch banks with five outputs may have five outputs. Eachoutput may be a combination of the direct current signals from the 32rectifier channel for one of the 5 switch bank output voltage levels.For example, if the voltage levels assigned to the switch bank outputsare 6 Volts, 10 Volts, 14 Volts, 18 Volts, and 22 Volts, the rectifiercircuit may have 6 Volt output that is connected to the 32 6 Voltoutputs of the 32 switch banks of the 32 rectifier channels, a 10 Voltoutput that is connected to the 32 10 Volt outputs of the 32 switchbanks of the 32 rectifier channels, a 14 Volt output that is connectedto the 32 14 Volt outputs of the 32 switch banks of the 32 rectifierchannels, a 18 Volt output that is connected to the 32 18 Volt outputsof the 32 switch banks of the 32 rectifier channels, and a 22 Voltoutput that is connected to the 32 22 Volt outputs of the 32 switchbanks of the 32 rectifier channels.

The MPPT may monitor the operation the rectifier, and may select whichof the switch bank's outputs should be used to output the direct currentsignal generated by the rectifier from the rectifier channel. Theselected output may be based on the voltage level that will maximize thepower transferred out of the rectifier channel. The MPPT may monitor therectifier and select a switch bank output in any suitable manner. Forexample, the MPPT may monitor the conduction angle of the rectifier,which may be the amount of time for which the rectifier is conducting,and select an output of the switch bank to maintain the conduction anglewithin a specified range. The MPPT may measure the open-circuit voltageof the alternating current signal at the rectifier input aftertemporarily disabling the rectifier, and may select a switch bank outputbased on some fraction of the measured open-circuit voltage at the inputof the rectifier. The MPPT may, instead of directly monitoring therectifier, iteratively select each of the available outputs of theswitch bank, measure the power transfer achieved through each output,and then select the output that exhibits the maximum power transfer. TheMPPT may select an output of the switch bank at any suitable intervaland at any suitable rate, and may leave an output selected for anysuitable length of time before selecting a different output.

The rectifier circuit and rectifier channels may be implemented in anysuitable manner. For example, each rectifier circuit may be implementedas an ASIC. Each rectifier channel may be implemented in the ASIC for arectifier circuit. The rectifier circuit ASICs may be installed on thesame PCB that includes the static input circuit and the power generationelements, for example, on a PCB layer on the opposite side of the PCBfrom the power generation elements.

The power receiver circuit may include a voltage bus. The voltage busmay include any suitable number of direct current inputs, of anysuitable voltage levels, connected to any suitable number of capacitorsor other forms of power storage. The number of direct current inputs tothe voltage bus may be the same as the number of the direct currentoutputs of a switch bank multiplied by the number of rectifier circuits.For example, the voltage bus may be connected to 4 rectifier circuits.The rectifier circuits may each have 32 channels, with switch banks withfive outputs. The voltage bus may include 20 direct current inputs tomatch the 20 total direct current outputs of the 4 rectifier circuits.The outputs from each rectifier circuit may be connected to one of thecapacitors of the voltage bus in parallel. For example, each of 4rectifier circuits may have 6 Volt outputs. The 6 Volt outputs from the4 rectifier circuits may be connected to a capacitor on the voltage bus.Each of the capacitors of the voltage bus may have its own directcurrent output from the voltage bus. The voltage of the direct currentsignal carried on the output of a capacitor may match the voltages ofthe direct current signals input into the capacitor from the rectifiercircuits. For example, a capacitor into which 6 Volt direct currentsignals are input may output a 6 Volt direct current signal. The numberof outputs from the voltage bus may be equal to the number ofcapacitors, which may in turn be equal to the number of outputs from aswitch bank of a rectifier channel. The voltage bus may be implementedin any suitable manner. For example, the voltage bus may be implementedon any suitable of layer of the PCB. The voltages of the direct currentsignal both input to and output from the capacitors may vary within arange of the voltages of the outputs from the rectifier circuits. Forexample, voltages of direct current signals carried on a 6 Volt outputfrom the rectifier circuit may vary over any suitable range around 6Volts, and the voltage of the direct current signal output of thecapacitor connected to the 6 Volt output may vary in a range around 6Volts. The range over which the voltage of the direct current signaloutput from the capacitor varies may be smaller than the range overwhich the voltage of the direct current signal input to the capacitorvaries.

The power receiver circuit may include any suitable number of voltageconverters. For example, the power receiver circuit may include a numberof DC/DC voltage converters equal to the number of outputs from thecapacitors of the voltage bus. Each DC/DC voltage converter may beconnected to the output of one of the capacitors of the voltage bus, andmay convert the direct current signal with that capacitor's outputvoltage to some specified, target, voltage. The target voltage may bethe same for all of the DC/DC voltage converters in the power receivercircuit. For example, a first DC/DC voltage converter may be connectedto a capacitor that outputs a 6 Volt direct current signal, and mayconvert that to a 5 Volt direct current signal. A second DC/DC voltageconverter may be connected to a capacitor that outputs a 10 Volt directcurrent signal, and may convert that to a 5 Volt direct current signal.The direct current signals output by the DC/DC voltage converters may becombined, resulting in a single direct current signal of the targetvoltage level that may be output from the power receiver circuit andused in any suitable manner, such as, for example, to power and suitableelectric or electronic device or circuit, such as a charging circuit fora battery. The DC/DC voltage converters may be implemented in anysuitable manner. For example, the DC/DC voltage converters may beswitching converters, and may be discrete converters, or may beintegrated.

Each DC/DC voltage converter may have an undervoltage lockout. Anundervoltage lockout may be connected in between the output of eachcapacitor of the voltage bus and each DC/DC voltage converter, and maybe any suitable device or mechanism for detecting voltage levels of theoutput from the capacitors and cutting off the direct current signalinput into the DC/DC voltage converters when the voltage drops too low,for example, below a threshold level, and reconnecting the directcurrent signal when the voltage is at or above the threshold level. Forexample, a capacitor may output a 10 Volt direct current signal. If thevoltage lockout detects that the output from the capacitor has droppedtoo far below 10 Volts, for example, due to the capacitor beingundercharged, the voltage lockout may disconnect the capacitor from theDC/DC voltage converter that converts the direct current signal from 10Volts to 5 Volts. The undervoltage lockout may reconnect that capacitorto the DC/DC voltage converter when the voltage output from thecapacitor has reached a suitable level, for example, within any suitablerange of or above 10 Volts. An undervoltage lockout may be set todisconnect and reconnect a DC/DC voltage converter from a capacitorbased on any suitable voltage threshold, and undervoltage lockoutsconnected to different voltage levels may have different thresholds.

In some implementations, each rectifier channel may include a rectifierand a single output. The outputs from the rectifier circuits may beconnected to a step down converter. The step down converter may receiveas input a direct current signal that is the combined output of all ofthe rectifier channels of all of the rectifier circuits, and may convertthe voltage of this direct current signal to a specified, targetvoltage, such as, for example, 5 Volts. The step down converter may useany suitable components for stepping down DC voltages, and may be ableto accept direct current signals over a wide range of voltages input andconvert these direct current signals to a direct current signal of thetarget voltage. The output of the step down converter may go to both alinear regulator and an output switch. The output of the output switchmay be the output for the power receiver circuit, and may be, forexample, connected to a charging circuit for a battery. When the outputswitch is closed, power may be delivered from the power receiver circuitto a circuit, such as the charging circuit, connected to the output. Theopening and closing of the output switch may be controlled by amicrocontroller.

The linear regulator may convert the direct current signal of the targetvoltage output by the step down converter to a direct current signalhaving a native voltage level for the microcontroller. The output of thelinear regulator may be connected to the microcontroller, powering themicrocontroller. The microcontroller may be any suitable electronicmicrocontroller, and may include an integrated analog-to-digitalconverter and radio. The microcontroller may monitor the operation ofthe power receiver circuit. For example, the microcontroller may monitorthe voltage (V_(RECT)) of the direct current signal being output fromthe rectifier circuits into the step down converter, the voltage(V_(LOAD)) of the direct signal being output from the step downconverter to the linear regulator and output switch, and the amperage(I_(LOAD)) of the direct current signal being output from the outputswitch. The microcontroller may use the radio to communicate with atransmitting device that transmits wireless power to the powergenerating mechanism, for example to report V_(RECT), V_(LOAD), andI_(OUT), so that the transmitting device may adjust the delivery ofwireless power to the power generating mechanism. The microcontrollermay control the opening and closing of the output switch, for example,through an enable/disable line connecting the microcontroller to theoutput switch.

The microcontroller may implement a state machine. The state machine mayinclude four states, a dead state, a handshake state, a standby state, acharge state. In the dead state, there may not be enough power tooperate the microcontroller. For example, the power generating mechanismmay not generate enough power to generate a direct current signal ofsufficient voltage through the step down converter and linear regulatorto operate the microcontroller, and a secondary source of power, such asa battery connected to a charging circuit connected to the powerreceiver circuit, may also not have enough power to operate themicrocontroller. In the dead state, if the power generating mechanismbegins to receive sufficient power from the transmitting device, thepower generating mechanism may begin to generate power in the form of analternating current signal. When the power generating mechanismgenerates sufficient power to raise the voltage of the direct currentsignal supplied to the microcontroller from the linear regulator tooperating levels, the microcontroller may generate a power-on-resetsignal and enter the handshake state.

In the handshake state, the microcontroller may use the radio tocommunicate with the transmitting device. The radio may communicate anysuitable data to the transmitting device, including, for example, dataregarding characteristics of the power generating mechanism that may beused by the transmitting device to adjust various aspects of powerdelivered to the power generating mechanism. For example, the radio maycommunicate data that indicates the presence of the power generatingmechanism, the location of the power generating mechanism, and mayauthenticate the power receiver circuit to the transmitting device,which may only transmit power to the power generating mechanisms ofauthenticated power receiver circuits. Once communication has beenestablished with the transmitting device, the microcontroller may enterthe standby state. The microcontroller may enter the standby state afterreceiving an instruction (TX_STBY) from the transmitting device.

In the standby state, the microcontroller may use the radio tocommunicate with the transmitting device. The communication may beperiodic, and may include any suitable data, such as, for exampleV_(RECT) and V_(LOAD) values as determined by the microcontroller. Thetransmitting device may use the data received from the microcontrollerto adjust the delivery of power to the power generating mechanism in anysuitable manner. For example, the transmitting device may adjust thephase, amplitude, focus, and steering of an ultrasonic beam directed atan ultrasonic transducer array. The transmitting device may determinethe minimum amount of power that can be delivered to the powergenerating mechanism to allow the power receiver circuit to output auseful amount of power. For example, the transmitting device maydetermine the minimum amount of power needed to allow the power receivercircuit to charge a device battery through a charging circuit thatreceives power output by the power receiver circuit. The transmittingdevice may, for example, compare received V_(RECT) values to apredetermined threshold for rectifier voltage (V_(RECT TH)), anddetermine the minimum power that can be delivered to the powergenerating mechanism to maintain V_(RECT)>V_(RECT) _(_) _(TH) at theinput of the step down converter from the rectifier circuits of thepower receiving circuit. When the transmitting device has determined theminimum power that it needs to deliver, the transmitting device mayinstruct the microcontroller to enter the charge state, for example,sending an appropriate command (TX_CHARGE), to the microcontrollerthrough the radio.

In the charge state, the microcontroller may cause the output switch toclose, allowing the power receiver circuit to deliver power to asuitable circuit, such as a charging circuit for a battery, connected tothe output of the output switch. The power delivered by the closedoutput switch may be a direct current signal having the same voltagelevel V_(LOAD) as the direct current signal output from the step downconverter, which may be, for example, 5 Volts, and may have amperageI_(LOAD). The microcontroller may continue to communicate with thetransmitting device through the radio while in the charge state. Forexample, the microcontroller may send V_(RECT), V_(LOAD), and I_(LOAD)values to the transmitting device, which may make adjustments to thepower delivered to the power generating mechanism to maintain V_(RECT),V_(LOAD), and I_(LOAD) at desired values.

The transmitting device may instruct the microcontroller exit the chargestate and return to the standby state, for example, sending anappropriate command (TX_STBY), to the microcontroller through the radio.The transmitting device may cause the microcontroller to exit the chargestate, for example, if the value of I_(LOAD) drops below a predeterminedthreshold, which may indicate that power is no longer needed by thecircuit connected to the output switch. For example, a battery beingcharged by a charging circuit connected to the output switch may befully charged. The transmitting device may cause the microcontroller toexit the charge state and enter standby if the transmitting deviceintends to stop delivering power to the power generating mechanism forany suitable reason. The microcontroller may also exit the charge stateif V_(LOAD) falls below a predetermined threshold (V_(LOAD) _(_) _(TH)_(_) _(FALL)), which may be an indication that step down converter canno longer maintain V_(LOAD) in regulation at the appropriate voltagelevel. The microcontroller may exit the charge state, enter the standbystate, and send a message indicating that V_(LOAD) dropped(RX_VLOAD_FAIL) to the transmitting device. Whenever the microcontrollerexits the charge state, the microcontroller may cause the output switchto open.

The microcontroller may return to the dead state from the handshakestate, standby state, and charge state. For example, the voltage (VDD)of the direct current signal supplied to the microcontroller through thelinear regulator may drop below a brown-out threshold (VDD_TH_FALL) forthe microcontroller, which may result in the microcontroller enteringthe dead state from whatever state it is in at the time the drop in VDDoccurs. Drops in VDD may occur, for example, due to interruption in thepower being delivered to the power generating mechanism from thetransmitting device. For example, an ultrasonic beam may be blocked fromreaching an ultrasonic transducer array by an obstructing object, or theamount of power delivered may be reduced due to environmentalinterference.

The power receiver circuit may be implemented using any suitablecombination of hardware and software. For example, components of thepower receiver circuit may be implemented in whole or in part as a fieldprogrammable gate array (FPGA) or application-specific integratedcircuit (ASIC) or complex programmable logic device (CPLD), or usingintegrated circuit packages. Components of the power receiver circuitmay be connected in any suitable manner. For example, connectionsbetween components may be implemented as traces on PCB, or using anyother suitable type of electrical connection for carrying alternatingcurrent signals and direct current signals. Voltage levels of directcurrent signals may be approximate, or within suitable ranges ofspecified voltage levels. For example, the direct signal output at thetarget voltage level may vary in any suitable range around the targetvoltage level.

FIG. 1 shows an example system suitable for a power receiver circuitaccording to an implementation of the disclosed subject matter. A powerreceiver circuit 100 may include transducer element array 110, a staticinput circuit 120, rectifier circuits 130 and 140, a voltage bus 150,and voltage conversion 160. The power receiver circuit 100 may be ableto receive power transmitted wirelessly, for example, through optical,ultrasonic, or RF transmission, using the transducer element array 110.

The transducer element array 110 may be a power generating mechanism forthe power receiver circuit 100. The transducer element array 110 mayhave a number of outputs for current equal to the number of elements inthe transducer element array 110. The elements of the transducer elementarray 110 may each output current to the static input circuit 120. Thestatic input circuit 120 may combine, in parallel, the currents outputfrom the elements of the transducer element array 110. The currents maycombined in any suitable manner. For example, the static input circuit120 may combine the currents output from separate groups of elements ofthe transducer element array 110, with each group of elements having itsown separate output from the static input circuit 120. The outputs ofthe static input circuit 120 may be connected to rectifier circuits,including the rectifier circuits 130 and 140. The current carried by theoutputs of the static input circuit 120 may be AC.

The power receiver circuit 100 may include any suitable number ofrectifier circuits. The outputs from the static input circuit 120 may bedivided among the available rectifier circuits, including the rectifiercircuits 130 and 140, in any suitable manner. For example, eachrectifier circuit may be connected to the same number of distinctoutputs from the static input circuit 120. Each rectifier circuit mayhave a number of outputs. Different outputs from the rectifier circuitsmay be assigned to carry current having different voltage levels. Thenumber of outputs, and the voltages they carry, may be the same for eachrectifier circuit. The outputs from the rectifier circuits may beconnected to the voltage bus 150. The current carried by the outputs ofthe rectifier circuits may be DC, converted from the AC input into therectifier circuits from the static input circuit 120.

The voltage bus 150 may include a number of outputs equal to the totalnumber of different voltage levels output by the rectifier circuits. Forexample, if the rectifier circuit 130 include a separate output for eachof five different voltage levels, the voltage bus 150 may include fiveseparate outputs. The voltage bus 150 may combine the outputs of therectifier circuits, including the rectifier circuits 130 and 140, byvoltage level. The outputs of the voltage bus 150 may be connected tothe voltage conversion 160.

The voltage conversion 160 may include a number of voltage converters.Each of the voltage converters in the voltage conversion 160 may receiveone of the outputs of the voltage bus 150, and convert the DC carried bythe output to DC of a set voltage level. For example, each voltageconverter may convert the received DC to 5 Volt DC. The outputs of thevoltage converters may be combined and output as a single current fromthe voltage conversion 160. The DC output from the voltage conversion160 may be used to provide power to another device or mechanism, suchas, for example, a charging circuit which may charge a battery.

FIG. 2 shows an example system suitable for a power receiver circuitaccording to an implementation of the disclosed subject matter. Thetransducer element array 110 may include transducer elements 201, 202,203, 204, 205, 206, 207, 208, 209, 210, 211, 212, 213, 214, 215, 216,217, 218, 219, 220, 221, 222, 223, and 224, which may be any suitabletype of transducers for receiving power transmitted wirelessly in anysuitable form. For example, the transducer elements 201-224 may beultrasonic transducers, which may convert ultrasonic sound waves intoAC. The transducer elements 201-224 may be grouped into a number ofgroups, which may include any suitable number of transducer elements inany suitable arrangement. For example, a group 250 may include thetransducer elements 201, 202, 205, and 206, which may form a 2×2 grid.Transducer elements in a group may be selected based on proximity, whichmay reduce the variation in the phase and amplitude of the AC generatedby the transducer elements in the group. For example, the transducerelements 201, 202, 205, and 206 may be ultrasonic transducers, and maygenerate AC with similar phase and amplitude when receiving ultrasonicsound waves from a transmitting device, as physical proximity may resultin the transducer elements 201, 202, 205, and 206 experiencing atransmitted ultrasonic wave in a similar manner.

FIG. 3 shows an example system suitable for a power receiver circuitaccording to an implementation of the disclosed subject matter. Thetransducer elements 201-224 of the transducer element array 110 may beconnected to the static input circuit 120. The static input circuit 120may include a separate group circuit, such as the group circuit 310 foreach group, such as the group 250, of the transducer elements 201-224,to connect the transducer elements of the group in parallel. Forexample, the outputs of each of the transducer elements 201, 202, 205,and 206 of the group 250 may be connected in parallel by the groupcircuit 310, which may output the combined output of the group 250 usingthe output 311. The output 311 may carry current that is the combinationof the AC generated by each of the transducer elements 201, 202, 205,and 206 of the group 250. Each group circuit of the static input circuit120 may include its own output, so that the number of outputs, such asthe output 311, from the static input circuit 120 may be equal to thenumber of transducer elements of the transducer element array 110divided by the number of transducer elements per group, such as thegroup 250. The static input circuit 120 may be implemented in anysuitable manner. For example, the static input circuit 120 may beimplemented with traces on any number of layers of a PCB which may alsoinclude the transducer element array 110. The outputs from transducerelements may be electrically connected to the static input circuit inany suitable manner. For example, traces and vias may be used to routeconnections through any number of layers of a PCB to connect each of thetransducer elements 201-224 to its group circuit in the static inputnetwork 120.

FIG. 4 shows an example system suitable for a power receiver circuitaccording to an implementation of the disclosed subject matter. Theoutput 311 of the static input circuit 120 may carry AC to the rectifiercircuit 130. The output 311 may be connected to a rectifier channel 450of the rectifier circuit 130. The rectifier channel 450 may include arectifier 410, an MPPT 420, and a switch bank 430. The rectifier 410 mayreceive the AC carried by the output 311, which may be the combined ACfrom the transducer elements 201, 202, 205, and 206, in the group 250.The rectifier 410 may convert the AC carried by the output 311 to DC.The rectifier may use a diode bridge, Schottky diodes, diode-connectedFETS, or may be any form of synchronous rectifier.

The voltage of the DC output by the rectifier 410 may be controlled bythe MPPT 420. The switch bank 430 may be connected to the output for therectifier 410, and may include any suitable number of direct currentoutputs 411 which may each be assigned a different voltage level. Thevoltage of the DC output by the rectifier 410 may be determined by theoutput 411 of the switch bank 430 selected by the MPPT 420. The MPPT 420may monitor the operation of the rectifier 410 and select an output ofthe switch bank 430 in any suitable manner. The selected output 411 maybe based on the voltage level that will maximize the power transferredout of the rectifier channel 450. The MPPT 420 may monitor theconduction angle of the rectifier 410 and select an output 411 of theswitch bank 430 in order to maintain the conduction angle within aspecified range, may measure the open-circuit voltage of the AC carriedby the output 311 to the rectifier 410 after temporarily disabling therectifier 410 and select an output 411 from the switch bank 430 based onsome fraction of the measured open-circuit voltage, or may, instead ofdirectly monitoring the rectifier 410, iteratively select each of theavailable outputs 411 of the switch bank 430, measure the power transferachieved through each of the outputs 411, and then select the output 411that exhibits the maximum power transfer. The MPPT 420 may select anoutput 411 of the switch bank 430 at any suitable interval and at anysuitable rate, and may leave an output 411 selected for any suitablelength of time before selecting a different output 411.

The switch bank 430 may receive DC output by the rectifier 410, and mayoutput the DC from the rectifier channel 450 using the output 411selected by the MPPT 420. The outputs 411 may be assigned any suitablevoltage levels. For example, the switch bank 430 may include fiveoutputs 411, which may be 6 Volts, 10 Volts, 14 Volts, 18 Volts, and 22Volts. The voltage level of the DC output by the rectifier 410 may bethe voltage level assigned to the output 411 selected by the MPPT 420.For example, if the MPPT 420 selects the output 411 assigned 14 Volts,the DC output by the rectifier 410 to the switch bank 430 may be, or bewithin any suitable range of, 14 Volts. The rectifier 410 may not outputat the voltage level of the selected output 411 immediately, forexample, if a capacitor that charges using the DC output by therectifier 410 is not sufficiently charged, and may reach the selectedvoltage when the capacitor has reached the appropriate charge level.

The rectifier 130 may have any suitable number rectifier channels, suchas the rectifier channel 450. Each rectifier channel may receive AC froma separate group circuit of the static input circuit 120, and may outputDC on an output selected from that rectifier channel's switch bank basedon voltage level by that rectifier channel's MPPT. The voltage levelsassigned to the outputs of the switch banks may be the same across eachrectifier channel of the rectifier circuit 130. The outputs of theswitch banks may be combined by assigned voltage level, so that thetotal number of outputs from the rectifier circuit 130 may be equal tothe number of distinct voltage levels assigned to the outputs 411. Forexample, if the switch bank 430 has five outputs 411, the rectifiercircuit 130 may have five outputs, which may combine the outputs 411 ofthe switch bank 430 with corresponding outputs assigned the same voltagefrom switch banks from other rectifier channels of the rectifier 130.For example, if the rectifier circuit 130 has ten rectifier channels andeach rectifier channel's switch bank has five outputs 6 Volts, 10 Volts,14 Volts, 18 Volts, and 22 Volts, the rectifier circuit 130 may havefive outputs at 6 Volts, 10 Volts, 14 Volts, 18 Volts, and 22 Volts. The6 Volt output from the rectifier channel may combine the 6 Volt outputsfrom the ten switch banks of the rectifier circuit 130, The 10 Voltoutput from the rectifier channel may combine the 10 Volt outputs fromthe ten switch banks of the rectifier circuit 130, and similarly for the14 Volt, 18 Volt, and 22 Volt outputs.

The rectifier circuit 130 and rectifier channels, such as the rectifierchannel 450, may be implemented in any suitable manner. For example, therectifier circuit 130 may be implemented as an ASIC. Each rectifierchannel, such as the rectifier channel 450 may be implemented in theASIC for the rectifier circuit 130. The ASIC for the rectifier circuit130 may be, for example, installed on the same PCB that includes thestatic input circuit 120.

FIG. 5 shows an example system suitable for a power receiver circuitaccording to an implementation of the disclosed subject matter. Thevoltage bus 150 may be connected to the outputs of the rectifiercircuits, such as the rectifier circuits 130 and 140. The voltage bus150 may include a number of capacitors equal to the number of outputsfrom each rectifier circuit. For example, the voltage bus 150 mayinclude capacitors 510, 520, 530, 540, and 550. Each of the capacitors510, 520, 530, 540, and 550 may receive all of the outputs from therectifier circuits at a particular voltage level. For example, if eachof the rectifier circuits has five outputs at 6 Volts, 10 Volts, 14Volts, 18 Volts, and 22 Volts, the capacitor 510 may receive all 6 Voltoutputs, the capacitor 520 may receive all 10 Volt outputs, thecapacitor 530 may receive all 14 Volt outputs, the capacitor 540 mayreceive all 18 Volt outputs, and the capacitor 550 may receive all 22Volt outputs. Each of the capacitors 510, 520, 530, 540, and 550 maycharge using the DC carried by the outputs from the rectifier circuits,and may output DC on the outputs 561. The voltage of the DC carried onthe output 561 for one of the capacitors 510, 520, 530, 540, or 550 maybe the voltage of the outputs from the rectifier circuits connected tothat capacitor when that capacitor is sufficiently charged.

FIG. 6 shows an example system suitable for a power receiver circuitaccording to an implementation of the disclosed subject matter. Theoutputs from the voltage bus 150 may carry DC to the voltage conversion160. The voltage conversion 160 may include a number of DC/DC convertersequal to the number of capacitors of the voltage bus 150. For example,the voltage conversion 160 may include DC/DC converters 610, 620, 630,640, and 650. The outputs from the voltage bus 150 may be connected toundervoltage lockouts, which may in turn be connected to the DC/DCconverters. For example, the undervoltage lockouts 611, 621, 631, 641,and 651 may each receive one of the outputs from the voltage bus 150,and may be connected to a respective one of the capacitors 610, 620,630, 640, and 650. The undervoltage lockouts 611, 621, 631, 641, and 651may detect voltage levels of the output from the capacitors 510, 520,530, 540, and 550, respectively, of the voltage bus 150, and maydisconnect respective DC/DC converter 610, 620, 630, 640, or 650 if thevoltage level drops below a threshold, and reconnect respective DC/DCconverter 610, 620, 630, 640, or 650 when the voltage level returnsabove the threshold. This may allow the undervoltage lockouts 611, 621,631, 641, and 651 to maintain the voltage levels assigned to theoutputs, such as the outputs 411, of each of the switch banks, such asthe switch bank 430, and cause the rectifiers, such as the rectifier410, to output DC at the voltage levels assigned to the outputscurrently selected from the switch banks connected to the rectifiers.

For example, the capacitor 510 may receive the 6 Volt outputs from therectifier circuits. The undervoltage lockout 611 may monitor the voltageof the DC output by the capacitor 510. The undervoltage lockout 611 maybreak the connection between the DC/DC converter 610 and the capacitor510 that goes through the undervoltage lockout 611 if the voltage levelof the DC output by the capacitor 510 falls below a threshold, which maybe 6 Volts, or may be under 6 Volts by any suitable amount. This mayallow the capacitor 510 to charge from the DC output by the rectifiercircuits. The undervoltage lockout may reconnect the DC/DC converter 610to the capacitor 510 when the voltage level of the DC output by thecapacitor 510 has returned to the threshold, or to some level above thethreshold, for example, after the capacitor is sufficiently charged. Theundervoltage lockout 611 may maintain the assigned voltage level betweenthe DC/DC converter 610, the 6 Volt output 411 of the switch bank 430that was assigned the voltage level of 6 Volts, and the rectifier 410when the MPPT 420 selects the 6 Volt output 411.

The DC/DC converters 610, 620, 630, 640, and 650 may convert DC atrespective voltage levels, for example, as set by the undervoltagelockouts 611, 621, 631, 641, and 651, to the DC of the same voltagelevel, which may be a target voltage level for the power receivercircuit 100. For example, The DC/DC converters 610, 620, 630, 640, and650 may convert, respectively, 6 Volt DC, 10 Volt DC, 14 Volt DC, 18Volt DC, and 22 Volt DC to 5 Volt DC. The DC of the same voltage leveloutput from the DC/DC converters 610, 620, 630, 640, and 650 may becombined and carried out of the voltage conversion 160 by the output661. The output 661 may carry DC at the target voltage level, forexample 5 Volts, out of the power receiver circuit 100 and to a circuitthat may utilize the DC in any suitable manner. For example, the output661 may carry DC to a charging circuit for a battery, where the DC maybe used to charge the battery. The DC carried by the output 661 may alsobe used, for example, to power any suitable electronic or electriccomponent, including, for example, microcontrollers, microprocessors,ASICS, FPGAs, actuators, switches, and motors.

FIG. 7 shows an example system suitable for a power receiver circuitaccording to an implementation of the disclosed subject matter. A powerreceiver circuit 700 may include the transducer element array 110, thestatic input circuit 120, rectifier circuits 730 and 740, a step downconverter 750, a linear regulator 760, an output switch 770, and acontroller 780. The power receiver circuit 700 may be able to receivepower transmitted wirelessly, for example, through optical, ultrasonic,or RF transmission, using the transducer element array 110.

The transducer element array 110 may have a number of outputs forcurrent equal to the number of elements in the transducer element array110. The elements of the transducer element array 110 may each outputcurrent to the static input circuit 120. The static input circuit 120may combine, in parallel, the currents output from the elements of thetransducer element array 110. The currents may combined in any suitablemanner. For example, the static input circuit 120 may combine thecurrents output from separate groups of elements of the transducerelement array 110, with each group of elements having its own separateoutput from the static input circuit 120. The outputs of the staticinput circuit 120 may be connected to rectifier circuits, including therectifier circuits 730 and 740. The current carried by the outputs ofthe static input circuit 120 may be AC.

The power receiver circuit 700 may include any suitable number ofrectifier circuits. The outputs from the static input circuit 120 may bedivided among the available rectifier circuits, including the rectifiercircuits 730 and 740, in any suitable manner. For example, eachrectifier circuit may be connected to the same number of distinctoutputs from the static input circuit 120. Each rectifier circuit mayhave a single output. The voltage carried by the output from eachrectifier circuit may vary. The outputs from the rectifier circuits maybe combined and connected to the step down converter 750. The currentcarried by the outputs of the rectifier circuits may be DC, convertedfrom the AC input into the rectifier circuits from the static inputcircuit 120.

The step down converter 750 may be any suitable step down converter ortransformer, and may convert the DC carried by the output from therectifiers, including the rectifiers 730 and 740, to a specified,target, voltage level. For example, the step down converter 750 mayconvert received DC of any voltage level to DC of 5 Volts. The output ofthe step down converter 160 may be connected to the linear regulator 760and the output switch 770.

The linear regulator 760 may convert DC received from the step downconverter 750 to a DC of a voltage level suitable for operating themicrocontroller 780. The microcontroller 780 may operate off the DCsupplied through the linear regulator 760, and may monitor variousvoltage and amperage levels of the power receiver circuit 700. Themicrocontroller 780 may control the output switch 770, enabling anddisabling the output switch 770.

The output switch 770 may be used to provide power to another device ormechanism, such as, for example, a charging circuit which may charge abattery. When the output switch 770 is enabled, DC from the step downconverter 750 may be allowed to exit the power receiver circuit 700through the output switch 770, where it may be utilized by anothercircuit. When the output switch 770 is disabled, no current may flow outof the power receiver circuit 700.

FIG. 8 shows an example system suitable for a power receiver circuitaccording to an implementation of the disclosed subject matter. Theoutput 311 of the static input circuit 120 may carry AC to the rectifiercircuit 730. The output 311 may be connected to a rectifier channel 850of the rectifier circuit 130. The rectifier channel 850 may include arectifier 810. The rectifier 810 may receive the AC carried by theoutput 311, which may be the combined AC from the transducer elements201, 202, 205, and 206, in the group 250. The rectifier 810 may convertthe AC carried by the output 311 to DC. The rectifier may use a diodebridge, Schottky diodes, diode-connected FETS, or may be any form ofsynchronous rectifier. The voltage of the DC output by the rectifier 810on the output 811 may be the voltage level that will maximize the powertransferred out of the rectifier channel 850.

The rectifier 730 may have any suitable number rectifier channels, suchas the rectifier channel 850. Each rectifier channel may receive AC froma separate group circuit of the static input circuit 120, and may outputDC on a single output. The outputs of the rectifier channels may becombined so that the rectifier circuit 730 has one output, which maycarry a DC current with a varying voltage. For example, the rectifiers,such as the rectifier 810, of the rectifier channels, may be connectedin serial through their outputs.

The rectifier circuit 730 and rectifier channels, such as the rectifierchannel 80, may be implemented in any suitable manner. For example, therectifier circuit 730 may be implemented as an ASIC. Each rectifierchannel, such as the rectifier channel 850 may be implemented in theASIC for the rectifier circuit 730. The ASIC for the rectifier circuit730 may be, for example, installed on the same PCB that includes thestatic input circuit 120.

FIG. 9 shows an example system suitable for a power receiver circuitaccording to an implementation of the disclosed subject matter. The stepdown converter 750 may be connected to the outputs, such as the output811, of the rectifier circuits, such as the rectifier circuits 730 and740. The step down converter 750 may receive the DC output from all ofthe rectifier channels, such as the rectifier channels 850 and 950, ofthe rectifier circuits, such as the rectifier circuits 730 and 740. Thestep down converter 750 may be a converter or transformer of anysuitable type, and may convert DC of any voltage level received from therectifier circuits to DC having a target voltage level, such as, forexample, 5 Volts. The step down converter 750 may output DC at thetarget voltage level. The output from the step down converter 750 may besplit, inside or outside of the step down converter 750, to outputs 961and 962. The DC input into the step down converter 750 from therectifier circuits may have a voltmeter connected in parallel that maybe used to measure the voltage of the output from the rectifiercircuits, V_(RECT).

FIG. 10 shows an example system suitable for a power receiver circuitaccording to an implementation of the disclosed subject matter. Thelinear regulator 760 may receive DC carried by the output 961 from thestep down converter 750. The linear regulator 760 may be any suitabledevice, component, or circuit to convert the DC output by the step downconverter 750 to DC of a native voltage level for the microcontroller780. The output of the linear regulator 760 may be connected to themicrocontroller 780. When the linear regulator 760 receives DC of anappropriate voltage level from the step down converter 750, the linearregulator 760 may output enough power at an appropriate voltage tooperate the microcontroller 780.

The output switch 770 may receive DC carried by the output 962 from thestep down converter 750. The output 1011 of the output switch 770 may bethe output for the power receiver circuit 700, and may carry DC whichmay be used by any suitable electric or electronic component, such as,for example, a charging circuit for a battery, microcontrollers,microprocessors, ASICS, FPGAs, actuators, switches, and motors. When theoutput switch 770 is closed, the output 1011 may carry DC out of thepower receiver circuit 700. When the output switch 770 is open, no DCmay be carried out of the power receiver circuit 700 on the output 1011.The opening and closing of the output switch 770 may be controlled bythe microcontroller 780.

The microcontroller 780 may be any suitable electronic microcontroller,and may include an integrated analog-to-digital converter and radio1050. The microcontroller 780 may be powered by DC from the linearregulator 760. The microcontroller 780 may monitor the operation of thepower receiver circuit 700. A voltmeter may be connected in parallelwith the step down converter 750, and may measure the voltage V_(RECT)of the DC being output from the rectifier circuits. The measurement ofthe voltage V_(RECT) of the DC being output from the rectifier circuits,such as the rectifier circuits 730 and 640, into the step down converter750, may be input into the microcontroller 780. The voltmeter formeasuring V_(RECT) may be implemented as part of the microcontroller780, or separately from the microcontroller 780, with themicrocontroller 780 receiving the measurements output by the voltmeter.A voltmeter may be connected in parallel with the output switch 770, andmay measure the voltage V_(LOAD) of the DC being output from the stepdown converter 750 to the output switch 770. The measurement of thevoltage V_(LOAD) of the DC being output from the step down converter 750may be input into the microcontroller 780. The voltmeter for measuringV_(LOAD) may be implemented as part of the microcontroller 780, orseparately from the microcontroller 780, with the microcontroller 780receiving the measurements output by the voltmeter. An ammeter may beconnected to the output 1011 from the output switch 770, and may measurethe amperage I_(LOAD) of the DC being output from the output switch 770.The measurement of the amperage I_(LOAD) of the DC being output from theoutput switch 770 may be input into the microcontroller 780. The ammeterfor measuring I_(LOAD) may be implemented as part of the microcontroller780, or separately from the microcontroller 780, with themicrocontroller 780 receiving the measurements output by the ammeter.

The microcontroller 780 may use the radio 1050 to communicate with atransmitting device that transmits wireless power to the transducerelement array 110, for example to report V_(RECT), V_(LOAD), andI_(OUT), so that the transmitting device may adjust the delivery ofwireless power to the transducer element array 110. The microcontroller780 may control the opening and closing of the output switch 770, forexample, through an enable/disable line. The microcontroller 780 mayopen and close the output switch 770 based on any suitable criteria,including, for example, based on instructions received through the radio1050, or based on the measurements of V_(RECT), V_(LOAD), and I_(OUT).

FIG. 11 shows an example arrangement suitable for a power receivercircuit according to an implementation of the disclosed subject matter.The microcontroller 780 may implement a state machine which may includea DEAD state 1102, HANDSHAKE state 1104, STANDBY state 1106, and CHARGEstate 1106. The microcontroller 780 may be in the DEAD state 1102 whennot enough power is delivered by the linear regulator 760 to operate themicrocontroller 780. For example, the transducer element array 110 maynot generate enough power to generate sufficient current and voltagethrough the step down converter 750 to operate the microcontroller 780.When the microcontroller 780 is in the DEAD state 1102, the outputswitch 770 may be open, and the output 1011 may not carry any currentout of the power receiver circuit 700. The microcontroller 780 may exitthe DEAD state 1102 and enter the HANDSHAKE state 1104 when sufficientpower is supplied to the microcontroller 780 by the linear regulator760. For example, when the transducer element array 110 generates enoughpower to provide DC of sufficient voltage to the microcontroller 780through the rectifier circuits, the step down converter 750, and linearregulator 760, the microcontroller 780 may generate a power-on-resetsignal and enter the HANDSHAKE state 1104.

In the HANDSHAKE state 1104, the microcontroller 780 may use the radio1050 to communicate with the transmitting device. The radio 1050 maycommunicate any suitable data to the transmitting device, including, forexample, data regarding characteristics of the transducer element array110 that may be used by the transmitting device to adjust variousaspects of power delivered to the transducer element array 110. Forexample, the radio 1050 may communicate data that indicates the presenceof the transducer element array 110, the location of the transducerelement array 110, and may authenticate the power receiver circuit 700to the transmitting device, which may only transmit power to thetransducer element array 110 of an authenticated power receiver circuit700. When the microcontroller 780 is in the STANDBY state 1104, theoutput switch 770 may be open, and the output 1011 may not carry anycurrent out of the power receiver circuit 700. Once communication hasbeen established with the transmitting device, the microcontroller 780may enter the STANDBY state 1106. The microcontroller 780 may enter theSTANDBY state 1106 in response to receiving an instruction, TX_STBY,from the transmitting device.

In the STANDBY state 1106, the microcontroller 780 may use the radio1050 to communicate with the transmitting device. The communication maybe periodic, and may include any suitable data, such as, for exampleV_(RECT) and V_(LOAD) values as determined by the microcontroller 780.When the microcontroller 780 is in the STANDBY state 1106, the outputswitch 770 may be open, and the output 1011 may not carry any currentout of the power receiver circuit 700. The transmitting device may usethe data received from the microcontroller 780 to adjust the delivery ofpower to the transducer element array 110 in any suitable manner. Forexample, the transmitting device may adjust the phase, amplitude, focus,and steering of an ultrasonic beam directed at an ultrasonic transducerarray. The transmitting device may determine the minimum amount of powerthat can be delivered to the transducer element array 110 to allow thepower receiver circuit 700 to output a useful amount of power. Forexample, the transmitting device may determine the minimum amount ofpower needed to allow the power receiver circuit 700 to charge a devicebattery through a charging circuit that receives power output by thepower receiver circuit 700 through the output 1011 of the output switch770. The transmitting device may, for example, compare received V_(RECT)values to the predetermined threshold for rectifier voltage V_(RECT)_(_) _(TH) and determine the minimum power that can be delivered to thetransducer element array 110 to maintain V_(RECT)>V_(RECT) _(_) _(TH) atthe output of the rectifier circuits, such as the rectifier circuits 730and 740. When the transmitting device has determined the minimum powerthat it needs to deliver, the transmitting device may instruct themicrocontroller 780 to enter the CHARGE state 1108, for example, sendingan instruction TX_CHARGE, to the microcontroller 780 through the radio1050.

In the CHARGE state 1108, the microcontroller 780 may cause the outputswitch 770 to close, allowing the power receiver circuit 700 to deliverpower to a suitable circuit, such as a charging circuit for a battery,connected to the output 1011 of the output switch 770. The powerdelivered by the closed output switch 770 through the output 1011 mayhave the same voltage level V_(LOAD) as the DC output from the step downconverter 750, which may be, for example, 5 Volts, and may have amperageI_(LOAD). The microcontroller 780 may continue to communicate with thetransmitting device through the radio 1050 while in the CHARGE state1108. For example, the microcontroller 780 may send V_(RECT), V_(LOAD),and I_(LOAD) values to the transmitting device, which may makeadjustments to the power delivered to the transducer element array 110to maintain V_(RECT), V_(LOAD), and I_(LOAD) at desired values.

The transmitting device may instruct the microcontroller 780 exit theCHARGE state 1108 and return to the STANDBY state 1106, for example,sending the command TX_STBY, to the microcontroller 780 through theradio 1050. The transmitting device may cause the microcontroller 780 toexit the CHARGE state 1108, for example, if the value of I_(LOAD) dropsbelow a predetermined threshold, which may indicate that power is nolonger needed by the circuit connected to the output 1011 of the outputswitch 770. For example, a battery being charged by a charging circuitconnected to the output 1011 of the output switch 770 may be fullycharged. The transmitting device may cause the microcontroller 780 toexit the CHARGE state 1108 and enter the STANDBY state 1106 if thetransmitting device intends to stop delivering power to the transducerelement array 110 for any suitable reason. The microcontroller 780 mayalso exit the CHARGE state 1108 if V_(LOAD) falls below thepredetermined threshold V_(LOAD) _(_) _(TH) _(_) _(FALL), which may bean indication that step down converter 750 can no longer maintainV_(LOAD) in regulation at the appropriate voltage level. Themicrocontroller 780 may exit the CHARGE state 1108, enter the STANDBYstate 1106, and send a message RX_VLOAD_FAIL indicating that V_(LOAD)dropped to the transmitting device. Whenever the microcontroller 780exits the charge state, the microcontroller 780 may cause the outputswitch 770 to open.

The microcontroller 780 may return to the DEAD state 1102 from theHANDSHAKE state 1104, STANDBY state 1106, and CHARGE state 1108. Forexample, the voltage VDD of the power supplied to the microcontroller780 through the linear regulator 760 may drop below the brown-outthreshold VDD_TH_FALL for the microcontroller 780, which may result inthe microcontroller 780 entering the DEAD state 1102 from whatever stateis in at the time the drop in VDD occurs. Drops in VDD may occur, forexample, due to interruption in the power being delivered to thetransducer element array 110 from the transmitting device. For example,an ultrasonic beam may be blocked from reaching an ultrasonic transducerarray by an obstructing object, or the amount of power delivered may bereduced due to environmental interference.

Embodiments of the presently disclosed subject matter may be implementedin and used with a variety of component and network architectures. FIG.12 is an example computer system 20 suitable for implementingembodiments of the presently disclosed subject matter. The computer 20includes a bus 21 which interconnects major components of the computer20, such as one or more processors 24, memory 27 such as RAM, ROM, flashRAM, or the like, an input/output controller 28, and fixed storage 23such as a hard drive, flash storage, SAN device, or the like. It will beunderstood that other components may or may not be included, such as auser display such as a display screen via a display adapter, user inputinterfaces such as controllers and associated user input devices such asa keyboard, mouse, touchscreen, or the like, and other components knownin the art to use in or in conjunction with general-purpose computingsystems.

The bus 21 allows data communication between the central processor 24and the memory 27. The RAM is generally the main memory into which theoperating system and application programs are loaded. The ROM or flashmemory can contain, among other code, the Basic Input-Output system(BIOS) which controls basic hardware operation such as the interactionwith peripheral components. Applications resident with the computer 20are generally stored on and accessed via a computer readable medium,such as the fixed storage 23 and/or the memory 27, an optical drive,external storage mechanism, or the like.

Each component shown may be integral with the computer 20 or may beseparate and accessed through other interfaces. Other interfaces, suchas a network interface 29, may provide a connection to remote systemsand devices via a telephone link, wired or wireless local- or wide-areanetwork connection, proprietary network connections, or the like. Forexample, the network interface 29 may allow the computer to communicatewith other computers via one or more local, wide-area, or othernetworks, as shown in FIG. 13.

Many other devices or components (not shown) may be connected in asimilar manner, such as document scanners, digital cameras, auxiliary,supplemental, or backup systems, or the like. Conversely, all of thecomponents shown in FIG. 12 need not be present to practice the presentdisclosure. The components can be interconnected in different ways fromthat shown. The operation of a computer such as that shown in FIG. 12 isreadily known in the art and is not discussed in detail in thisapplication. Code to implement the present disclosure can be stored incomputer-readable storage media such as one or more of the memory 27,fixed storage 23, remote storage locations, or any other storagemechanism known in the art.

FIG. 13 shows an example arrangement according to an embodiment of thedisclosed subject matter. One or more clients 10, 11, such as localcomputers, smart phones, tablet computing devices, remote services, andthe like may connect to other devices via one or more networks 7. Thenetwork may be a local network, wide-area network, the Internet, or anyother suitable communication network or networks, and may be implementedon any suitable platform including wired and/or wireless networks. Theclients 10, 11 may communicate with one or more computer systems, suchas processing units 14, databases 15, and user interface systems 13. Insome cases, clients 10, 11 may communicate with a user interface system13, which may provide access to one or more other systems such as adatabase 15, a processing unit 14, or the like. For example, the userinterface 13 may be a user-accessible web page that provides data fromone or more other computer systems. The user interface 13 may providedifferent interfaces to different clients, such as where ahuman-readable web page is provided to web browser clients 10, and acomputer-readable API or other interface is provided to remote serviceclients 11. The user interface 13, database 15, and processing units 14may be part of an integral system, or may include multiple computersystems communicating via a private network, the Internet, or any othersuitable network. Processing units 14 may be, for example, part of adistributed system such as a cloud-based computing system, searchengine, content delivery system, or the like, which may also include orcommunicate with a database 15 and/or user interface 13. In somearrangements, an analysis system 5 may provide back-end processing, suchas where stored or acquired data is pre-processed by the analysis system5 before delivery to the processing unit 14, database 15, and/or userinterface 13. For example, a machine learning system 5 may providevarious prediction models, data analysis, or the like to one or moreother systems 13, 14, 15.

The foregoing description, for purpose of explanation, has beendescribed with reference to specific embodiments. However, theillustrative discussions above are not intended to be exhaustive or tolimit embodiments of the disclosed subject matter to the precise formsdisclosed. Many modifications and variations are possible in view of theabove teachings. The embodiments were chosen and described in order toexplain the principles of embodiments of the disclosed subject matterand their practical applications, to thereby enable others skilled inthe art to utilize those embodiments as well as various embodiments withvarious modifications as may be suited to the particular usecontemplated.

The invention claimed is:
 1. A power receiver circuit device comprising:a voltage bus comprising two or more capacitors; two or moreundervoltage lockouts, each undervoltage lockout having an inputconnected to one of the capacitors and an output, each of the two ormore undervoltage lockouts configured to disconnect its output when avoltage level input to the undervoltage lockout drops below apredetermined threshold, and wherein the predetermined threshold isdifferent for at least two of the two or more undervoltage lockouts; andtwo or more DC/DC converters, each DC/DC converter connected to one ofthe undervoltage lockouts, each DC/DC converter configured to convert adirect current signal of a predetermined voltage level to a directcurrent signal of a target voltage level, wherein the predeterminedvoltage level is different for at least two of the two or more DC/DCconverters.
 2. The device of claim 1, wherein the capacitors of thevoltage bus receive direct current from one or more rectifiers.
 3. Thedevice of claim 1, wherein at least one of the two or more capacitorsreceive direct current of a different voltage than at least one other ofthe two or more capacitors.
 4. The device of claim 1, wherein one of thetwo more undervoltage lockouts is connected to one of the two or morecapacitors, and wherein the undervoltage lockout is further connected toone of the two or more DC/DC converters.
 5. The device of claim 4,wherein the one of the two or more undervoltage lockouts is configuredto disconnect its output into the one of the two or more DC/DCconverters when a voltage level of a direct current signal input to theone of the two or more undervoltage lockouts drops below thepredetermined threshold for the one of the two or more undervoltagelockouts.
 6. The device of claim 4, wherein the one of the two or moreDC/DC converters is configured to convert a direct current signal of thepredetermined voltage level to a direct current signal of the targetvoltage level.
 7. The device of claim 1, further comprising a powergenerating mechanism comprising power generating elements that generatealternating current signals that are converted into direct currentsignals input to the two or more capacitors.
 8. The device of claim 7,wherein the power generating mechanism comprises a transducer array, andwherein the power generating elements comprise transducers.
 9. Thedevice of claim 8, wherein the transducer array is an ultrasonictransducer array, and wherein the transducers are ultrasonictransducers.
 10. The device of claim 7, wherein the power generatingmechanism comprises a radio frequency array.
 11. A power receivercircuit device comprising: a step down converter connected to one ormore rectifier circuits, the step down converter configured to convert adirect current signal to a direct current signal of a target voltagelevel; an output switch connected to the step down converter; a linearregulator connected to the step down converter; a microcontrollerconnected to the linear regulator and the output switch and configuredto control the output switch.
 12. The device of claim 11, wherein thelinear regulator is configured to convert a direct current signal fromthe step down converter to a direct current signal with a native voltageof the microcontroller.
 13. The device of claim 11, wherein themicrocontroller is configured to control the output switch by openingthe output switch and closing the output switch.
 14. The device of claim11, wherein the microcontroller further comprises a radio configured tocommunicate with a transmitting device.
 15. The device of claim 14,wherein the microcontroller is configured to communicate with thetransmitting device using the radio when the linear regulator suppliessufficient power to operate the microcontroller.
 16. The device of claim15, wherein the communication with the transmitting device comprises oneor of sending a measurement of a voltage of a direct current signalinput into the step down converter, sending a measurement of a voltageof a direct current signal input to the output switch, sending ameasurement of an amperage of a direct current signal output by theoutput switch, sending a message indicating that voltage of the directcurrent input to the output switch has fallen below a predeterminedthreshold, receiving a message instructing the microcontroller to openthe output switch, and receiving a message instructing themicrocontroller to close the output switch.
 17. The device of claim 11,wherein the output switch is configured to output a direct currentsignal received from the step down converter when the output switch isclosed and to output no signal when the output switch is open.
 18. Thedevice of claim 11, wherein the step down converter is furtherconfigured to receive the direct current signal from the one or morerectifier circuits.
 19. The device of claim 18, wherein the directcurrent signal from the one or rectifier circuits has a varying voltage.20. The device of claim 18, further comprising a power generatingmechanism that generates one or more alternating current signals outputto the one or more rectifier circuits.